Yea I bought an S2A-O (-O version has the longer 27" X travel get that if you can). But mine was very neglected. As a result I've put lots of parts in it. I'm not complaining because I got it pretty cheap and now it's a pretty decent machine. All the parts I have have needed have been available and Yamazen had in stock. They don't give them away but the prices are pretty decent. For example, I decided to replace the spindle. Bearings sounded good but it had about .001 runout. I could have had it ground maybe but a whole new spindle was $2500. I never heard of a cnc mill you can put a new spindle in for that. And it took me about 2 hours to boot. That's the other real up side to these machines very easy to work on yourself.
If i was buying another and could look it over before I bought, best if you can take the Y axis way cover off the front and look things over. It seems with mine they let chips build up and get up into the Y axis ball screw and linear bearings. You can also take your phone and reach under and take some photos if you can't take it off. Can also look in from the chip pan side with a flash light. The other thing I bought a Maritool 30 taper test probe tool and just keep it as my sort-of gold standard tool for checking the spindle runout. If you could buy one of those and put in to check things. If it an auction you probably can't do some of that but those are the areas I'd check.
The big limitation is that these are really just 2.5 axis machines and memory is limited. Some of them you can upgrade the firmware and add drip feeding capability (I did this) but the parts I am making in that machine are 5 op parts and I can get all the program in the memory, just barely, so don't need to drip feed.
